The p38 kinase is a mitogen-activated protein (MAP) kinase that belongs to the serine/threonine kinase superfamily. This kinase is activated by extracellular stresses such as heat, UV light, and osmotic stress, as well as by inflammatory stimuli such as lipopolysaccharide. When activated, p38 kinase phosphorylates intracellular protein substrates that regulate the biosynthesis of the pro-inflammatory cytokines tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β). These cytokines are implicated in the pathology of a number of chronic inflammatory disorders (Lee, et al., Ann. N.Y. Acad. Sci., 696, 149-170 (1993); Muller-Ladner, Curr. Opin. Rheumatol., 8, 210-220 (1996)), cardiovascular and central nervous system disorders (Salituro, et al., Current Medicinal Chemistry, 6, 807-823 (1999)), and autoimmune disorders (Pargellis, et al., Nature Structural Biology, 9(4), 268-272 (2002)). In addition, the phosphorylated form of mitogen-activated protein kinase-protein kinase 2 (or pMAPKAPK2) is also a kinase in the p38 MAPK pathway and can be directly activated by p38 MAPK. Mouse knockout studies of MAPKAPK2 show a reduction in cytokine production suggesting MAPKAPK2 can be a key regulator of the inflammatory response and can also be a potential target for anti-inflammatory therapy (WO 2005120509).
A number of urea compounds (for example in WO 9923091, WO 01012188, WO 04004720, WO 04037789, WO 99/32111, US 2004/0058961, EP 1609789, WO 03072569 and WO 0043384) have been identified as p38 kinase inhibitors or cytokine inhibitors. P38 kinase inhibitors or cytokine inhibitors may be costly to produce and may have bioavailability and absorption problems that limit the in vivo effects and therapeutic use. Therefore a need exists for new small molecule cytokine suppressive drugs, i.e., compounds that are capable of inhibiting p38 kinase with improved potency and greater bioavailability.
The present invention provides new inhibitors of p38 kinase useful for the treatment of conditions resulting from excessive cytokine production.